Abstract

Schlieren diagnostics of cathodic arc flows in air are presented. Three important processes are observed: (1) a luminous hemispherical region near the cathode with a radius of ≈1 mm, identified as the cathodic metallic plasma; (2) a luminous plasma jet extending ≈10 mm from the cathode, termed as the cathodic air jet (CAJ); (3) a background gas pushed to expand at subsonic velocities ≥100 m/s. The gas is accelerated in the direction of the CAJ. The main collisional processes in the CAJ are identified using optical emission spectroscopy and mean free path analysis. The CAJ plasma is shown to be composed of and Cu+ ions. It is concluded that the CAJ length is determined by the dissociative recombination of . With external magnetic field, the CAJ rotates according to the Lorentz force direction. Observing the CAJ motion and its affect on stationary and flowing background gas, it is concluded that the CAJ has significant directed thrust.